1. Field of the Invention
This invention relates to a flow meter, and more particularly to a flow meter of this kind which is capable of eliminating flow disturbance and generating stable detected signals even with a high flow rate.
2. Description of the Prior Art
In conventional flow meters employing a microbridge sensor, the sensor is simply placed at a location on the inner wall of a flow passage in a predetermined shape such as a circular or rectanglar pipe.
The above structure, that is, placing a microbridge sensor on the inner surface of the wall of the circular or rectangular flow path, allows measurement of flow at a low rate. However, as the flow rate is increased, disturbance is produced in the flow due to the difference in the passage diameter at the upstream side, curvature of the passage, the wall surface, and so on, whereby a rapidly responding sensor such as the microbridge sensor responds to such disturbance and accordingly its output signal is correspondingly disturbed. It is therefore necessary to provide a strong low pass filter to remove noise components and measure an average flow. Also, if an available electric power is limited, the sensor has to be driven intermittently, so that a disturbed output makes the measurement quite difficult.